Answer:
$16.8
Step-by-step explanation:
If topaz cost $8 per kilogram, hence;
1 kg = $8
To calculate how much money is 2 1/10 kilograms​, we can write;
2 1/10 = $x
Divide both expressions
1/(21/10) = 8/x
10/21 = 8/x
Cross multiply
10x = 8*21
10x = 168
x = 168/10
x = 16.8
Hence 2 1/10kg of topaz will cost $16.8